Update comments on legacy Configuration/Platform check
Update comments on legacy Configuration/Platform check

Adjust the wording to make it simple, brief and clear.

Co-Authored-By: Rainer Sigwald <raines@microsoft.com>

> Fixup with original commit when this patch is approved.

AndyGerlicher/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,mono/msbuild,mono/msbuild,mono/msbuild,sean-gilliam/msbuild,AndyGerlicher/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,mono/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild